Most renovation schedules treat the aircon as one line and one visit. The tiler comes, the carpenter comes, the painter comes, and somewhere in there the aircon people come and put the units up. That is not how it works, and the gap between how it is scheduled and how it actually happens is where a surprising amount of money gets lost.
Aircon is one of the few trades on a Singapore renovation that has to come twice. The first visit happens early, before things are closed up, and almost none of it is visible when it is done. The second visit happens near the end and is the only part most homeowners ever see. Get the first one in the wrong place in the programme and the second one still happens on schedule — it just happens on top of a problem that will surface in the second year.
The two visits, and why the first one is the important one
The first fix is the copper refrigerant piping, the condensate drain line, the sleeves through walls, the marking out of where each indoor unit sits and where the condenser goes. On most jobs this is the work that ends up inside a false ceiling, inside a bulkhead, or buried in a wall.
The second fix is mounting the indoor units, setting the condenser, connecting up, vacuuming and charging the system, and testing. This one is quick and clean and looks like the whole job.
Everything that can go badly wrong is decided during the first fix, and almost all of it becomes unreachable immediately afterwards. That is the entire argument for taking the sequence seriously.
Drainage fall — the mistake that costs the most
An indoor unit produces condensate whenever it runs, and that water leaves through a drain pipe that has to run downhill the whole way to wherever it discharges. There is no pump on a standard installation to rescue a bad route. The fall is either there or it is not.
Here is how it goes wrong. The ceiling design gets finalised first, because it is the visible thing everyone is discussing. Beam positions, bulkhead depths and light coves get fixed. Then the aircon installer arrives and finds that the only remaining path from the bedroom unit to the discharge point has to cross under a beam and then come back up, or run dead flat for four metres.
What happens next is the part worth knowing: the system will pass its test and work perfectly for a while. Water sits in the flat section, dust and biological growth collect there, the passage narrows, and eventually the pan backs up and overflows — through a ceiling that has by then been skim-coated and painted twice. The repair is not the pipe. The repair is the ceiling.
If you take one thing from this article: the drain route and its fall should be agreed before the ceiling design is frozen, not after. Ask to be shown, on the ceiling plan, where each drain runs and which direction it falls.
What has to be decided before the carpenter starts
If any indoor unit is going into a bulkhead, a recess or a boxed-in section, the actual model has to be confirmed first. Indoor units are not a standard size across brands or even across a single brand's range, and the drain outlet and pipe entry are not in the same position on every one of them.
A bulkhead built to a guessed dimension is a common and entirely avoidable problem. It usually resolves in one of two unsatisfying ways: the unit gets swapped for whatever fits the hole rather than whatever suits the room, or the carpentry gets cut about after it has been finished. Neither is what you paid for. If you are still comparing systems, our guide to choosing between a System 3, 4 or 5 is the decision that needs to happen before, not after, the joinery is drawn.
The electrician has to know before the wall closes
Each system needs a power supply and an isolator, and those positions have to be in the electrician's first fix. Wiring gets chased into walls and buried early. If the aircon layout moves after that — one more unit, a different wall, the condenser relocated — you are either opening the wall again or running surface trunking somewhere visible.
This is the single most common reason a renovation ends up with a length of white trunking running across a bedroom wall that nobody planned for. It is not that the electrician did anything wrong. It is that the aircon layout was still moving when the wiring was already permanent.
Where the condenser goes, and when that has to be settled
The condenser position needs to be fixed before the ledge, balcony or service yard finishes are laid, because brackets have to be drilled and the piping has to arrive there through a sleeve that was cast or cored earlier.
In an HDB flat the position is also constrained by what is actually permitted, which is a separate question from what is physically possible — worth reading our note on what the aircon ledge allows and what to check before you commit, particularly if you are buying and have not collected keys. On a landed property or a condo the constraint is more often access for future servicing and how far the pipe run has become.
Test the concealed piping while you can still see it
Once the piping is inside a ceiling or a wall, a leak on that run is difficult to find and expensive to reach. While it is still exposed, it is trivially easy to check.
Ask for the pressure test to be carried out and witnessed before anything is closed up, and take photographs of the pipe and drain routes before the boards go on. Keep those photos. If anything ever has to be opened up in that ceiling — for aircon or for anything else — knowing exactly where the refrigerant piping runs is the difference between a small opening and a large one.
Leave the access you will need in year three
A bulkhead built tight around an indoor unit looks immaculate on handover day. It also means that every future service takes longer, costs more, and in the worst cases cannot be done properly at all without taking carpentry apart.
What you need is enough room that the front panel opens fully, the filters come out, and the drain pan and blower can actually be reached. This is not a large amount of space, but it has to be deliberate — it does not happen by accident, and no one will leave it unless you ask.
Ask to be shown the access before the bulkhead is closed, not told about it. Open the panel yourself while the trade is still on site. It is a two-minute check that determines what every service visit for the next decade will cost you.
A workable order
- Confirm the system and the actual unit models, and where each indoor unit and the condenser will sit.
- Mark those positions on the ceiling and electrical plans, with the drain routes and the direction of fall shown.
- Aircon first fix: piping, drain lines, wall sleeves. Electrician's first fix in the same window, with isolator positions already agreed.
- Pressure test the concealed pipework, witness it, photograph the routes.
- Ceiling, bulkheads, plastering, carpentry — with the service access left open and checked.
- Painting.
- Aircon second fix: units mounted, system vacuumed and charged, tested, handed over.
The order matters more than the dates. A renovation that slips by two weeks is an inconvenience. A renovation where the ceiling closed before the drain fall was resolved is a repair.
What to ask for, today
If your renovation has not started, ask for a marked-up ceiling plan showing unit positions, drain routes with fall direction, condenser position and isolator positions. If it has started but nothing is closed up yet, ask for the same thing now — it is still cheap.
If the ceiling is already closed and you were never shown any of this, the useful thing is not to open it up. It is to know where the piping runs and to have the drain checked properly at the first service, before a slow problem becomes a visible one.
It is also worth understanding who is actually carrying the responsibility for all of this, which is a different question depending on how you bought the system — we went through that in buying your aircon through the ID or direct.
If you want the sequence checked
If you are mid-renovation and not sure whether the aircon has been sequenced properly, send us where you are in the programme and we will tell you honestly what is still recoverable and what is not. Our installation page covers what a standard installation includes.
WhatsApp us on 9107 2601 — usually a reply within five minutes.